The present invention relates to a power feeding system and a power feed control method and relates to, for example, a power feeding system and a power feed control method that select one of a plurality of power supply voltages set in a USBPD standard and perform a power feeding operation.
In recent years, many electronic devices such as personal computers, smartphones, and tablet terminals include a Universal Serial Bus (USB) interface. These electronic devices are able to perform data communications with other electronic devices via the USB interface and to receive power from the other electronic devices.
In accordance with the introduction of the USB power delivery (hereinafter it will be referred to as a USBPD) standard, a plurality of power supply voltages have been selectively supplied to one power supply line (Universal Serial Bus Power Delivery Specification Revision 2.0, Version 1.1 (May 7, 2015)). In the USBPD standard, the power feeding direction is not fixed and each component that constitutes a USBPD system such as a USB host, a USB hub, a battery charger, and a cable becomes a source-side device which supplies power via a power supply line (device that supplies the power supply voltage) or a sink-side device which receives power via the power supply line (device that receives the power supply voltage) depending on a communication partner.
The USBPD device selects, for example, one of power supply voltages of 5 V, 12 V, and 20 V depending on the communication partner and supplies the selected power supply voltage to the communication partner via the power supply line. Further, in the cable that connects the USBPD devices, a specification for mounting an ID chip is standardized (Universal Serial Bus Type-C Cable and Connector Specification Revision 1.1 (Apr. 3, 2015)). The ID chip stores specification information on the cable such as the current capacity, the performance thereof, and the vendor recognition information thereon. Such a cable is called an Electronically Marked Cable (E-marked cable).
The specification information on the cable is reported to the USBPD device from the ID chip mounted on the cable together with a Start Of Packet (SOP′) packet, which indicates the start of the sequence. The SOP′ packet is recognized by the source-side device of the USBPD device. Since the source-side device supplies the power supply voltage by referring to the current capacity of the cable based on the specification information on the cable, it is possible to avoid heating of the cable due to an overcurrent.